The obliquity of the ecliptic.

In view of the discrepancy between observed and calculated secular rates of change in the mean apparent obliquity of the ecliptic, a reassessment of observed values of the obliquity of the ecliptic is made. Least-squares adjusted values of the obliquity are derived for a number of epochs (1000 B.C. to A.D. 2000). A simple numerical expression for the obliquity is given which supersedes the standard expression and amply approximates the expected cyclic behavior for a time span of at least 1 million years.